There have not been any posts for some time concerning dry washing with wood chips and/or sawdust. I have been happily producing biodiesel for a number of years using a BioPro 190 and water washing. I need to move away from water washing because disposing of the water has become an issue. I live in the country and the soaps do not do well in my septic tank.I am seriously considering fabbing up a 55gal steel drum sawdust dry wash system utilizing an open top drum with a band clamp. I have an unlimited supply of sawdust from a bandmill and various wood working equipment.I would appreciate hearing from folks that have been using such a system for a while. Specifically if anyone has had problems maintaining the lid seal, spontaneous combustion, screen clog ging, etc..

I began dry washing with tropical hardwoods a couple years ago with great results. I get an unlimited supply from a nearby furniture maker. I placed an inverted colander covered with some screen over the bung of a barrel with the bottom cut out, the bottom now the top and the bung fitted with a valve at the bottom. The barrel is filled a few inches from the top with the sawdust/shavings and another screen tucked in over that. I fill the barrel with bio until level with the top screen and let it set. I'll drain a couple buckets occasionally and dump it back in the top of the barrel. More often if I'm trying to hurry the process. I don't have a set time but have cycled the bio out the valve and back in the top in a day but usually do this process in three or more days. My preference is to also do a quick water wash. I mist spray a few gallons, dump that, the water comes out clear, then mist once more and bubble wash with that water. The water is usually still clear but I do another 10 minute mist and let everything settle before drying. I've used the same sawdust for several hundred gallons. I never drain all the bio from the sawdust barrel until I'm sure I'll be refilling it within a day, to prevent spontaneous combustion. I've read some people don't water wash using sawdust/shavings/chips but I think it is a little insurance and a way of checking how clean it is. I probably use 80% less water now. I burn the well drained sawdust when heating the glycerin to make soap and a couple neighbors burn the rest for cooking.

Originally posted by Dgs:Surely Jon the intention is that the soaps get absorbed (or it could be adsorbed) into the media.I am not sure that the intent is for the soap to be absorbed into the wood so much as the intent is to remove the soap and glycerine from the bio.If they are 'free' in the media then it doesn't matter which way round the flow is, they will still come out with the bio.No that is not true at all, based on solid evidence.Not trying to be pedantic here, just trying to understand your reasoning.

This is not based on reasoning but rather personal experience.I use a 205l drum full of chips which I originally setup in a down-flow configuration. I found that after only passing a few batches through it that my test samples from the chips had more soap in them then just settled bio without the chip treatment. This led me to try to run the same drum in an upflow which produced samples with zero soap for the rest of the year.It is also very evident when I empty the drums, at least the bottom 1/3 is dense with slimy white soap as well as glycerine at the very bottom. The soap and glycerine absolutely settle to the bottom of the chip drum and the fuel coming out of the top is soap free.Perhaps the chips cause the soap and glycerine to readily separate from the bio. I would suggest whats actually happening is that the wood sucks all the remaining trace methanol from the bio which automatically would make the soap and glycerine precipitate out much faster/easier.Cheers,Jon

Originally posted by Dgs:After de-mething (aquarium bubbler for 24 hours) then settling for 24 hours, the soap level is no more than 300ppm. One pass through the shavings reduces the soap to zero.

Hi Dgs,

Firstly hello from Indonesia here, and secondly sorry if you don't mind I have lots of questions regarding the the bubbler method :

1. How do you find the aquarium bubbler de-mething method? Is it really efficient at removing methanol?2. Does it affect the oxidation stability numbers much?3. How exactly do you do the bubbler method e.g. what types of hoses and diffuser do you use that won't melt in the bio, how powerful is the pump, etc?4. What is your original soap levels prior to bubbling? Do you use UCO as feedstock?

If anyone can weigh in with their experiences that would be great too.

Originally posted by Dgs:Surely Jon the intention is that the soaps get absorbed (or it could be adsorbed) into the media.I am not sure that the intent is for the soap to be absorbed into the wood so much as the intent is to remove the soap and glycerine from the bio.If they are 'free' in the media then it doesn't matter which way round the flow is, they will still come out with the bio.No that is not true at all, based on solid evidence.Not trying to be pedantic here, just trying to understand your reasoning.

This is not based on reasoning but rather personal experience.I use a 205l drum full of chips which I originally setup in a down-flow configuration. I found that after only passing a few batches through it that my test samples from the chips had more soap in them then just settled bio without the chip treatment. This led me to try to run the same drum in an upflow which produced samples with zero soap for the rest of the year.It is also very evident when I empty the drums, at least the bottom 1/3 is dense with slimy white soap as well as glycerine at the very bottom. The soap and glycerine absolutely settle to the bottom of the chip drum and the fuel coming out of the top is soap free.Perhaps the chips cause the soap and glycerine to readily separate from the bio. I would suggest whats actually happening is that the wood sucks all the remaining trace methanol from the bio which automatically would make the soap and glycerine precipitate out much faster/easier.Cheers,Jon

Hi Jon,

Can you elaborate on your upflow method? I just watched the video by fuelfarmer on Youtube about using drums as sawdust filters and it looks simple enough to build. However the upflow method you mentioned sounds a lot less hassle and more efficient. Is it applicable using 200 litre drums as well and how easy is it to construct?

The bubble method is efficient at removing methanol as long as it is left long enough. You have, however to be aware of the danger of methanol fumes.

I have no idea how it effects the oxidation stability.

The hoses are just 6mm pvc tubing which bubble through a 'sander' air diffuser, made of wood, it puts out many times more very tiny bubbles than an airstone.

My soap levels post last reaction are in the region of 5000ppm and after just settling for a couple of hours will reduce by 2000ppm or so.

As the bubbling continues and the methanol content decreases the biodiesel is not able to hold the soap/glycerol in suspension and so it will drop to the tank bottom.

I use mostly KOH as a catalyst and so the soap level is difficult to reduce to less than 200ppm by the bubble/settle method. if NaOH is the catalyst then the soap levels will be reduced.

I do use UCO as the feedstock.

Cheers, Dave.

Hi Dave,

Thanks for the quick and very helpful reply.

I also use KOH, and it's reassuring to see that my soap levels post-reaction is very similar to yours (5000 ppm), and to hear that there is hope in the bubbling method to decrease it even to levels as low as 200 ppm.

The only difference to what you're doing is that I immediately demethylate using heat and turbulence post-reaction, catching the methanol with a condenser, then settle the glycerin after. Even after demethylation and settling the biodiesel for hours after transferring it to a holding tank, the soap levels remain high in the 5000 ppm level, unlike yours which drops to 2000 ppm after settling.

I think I will give the bubbler method a try, and with the absence of methanol the soap should drop out faster than usual, right?

Btw, in your opinion, how many air diffusers would I need to aerate a 1000-litre tote tank and what kind of pump should I use?

Can you elaborate on your upflow method? I just watched the video by fuelfarmer on Youtube about using drums as sawdust filters and it looks simple enough to build. However the upflow method you mentioned sounds a lot less hassle and more efficient. Is it applicable using 200 litre drums as well and how easy is it to construct?

Hi Riz,I just pump the fuel into the bottom of the 55 gallon drum and made a screen over the outlet at the top. I use a metering pump to pump it through the chips. I made a bubbler for my 1000L tote out of some 3/8" copper tube, I drilled a bunch of 1/16" holes in it and I run it from my rocker style pond compressor. It works great and I have not any issues with stability.Cheers,Jon

I recognize that dry washing using magnesium silicate powder is different than wood chips purification of biodiesel. Magnesium silicate absorbs more polar molecules rather than less polar ones. For the purpose of producing a superior, purified biodiesel product it's economical to use magnesium silicate for small amounts. I remove excess alcohol from crude biodiesel after removing the lower glycerine layer. I remove alcohol by vacuum distillation. Depending on soap levels I added magnesium silicate powder with fast stirring at just below the boiling point of the alcohol for thirty minutes or so. Any free fatty acids, soaps and other impurities are also removed. I expect traces of water might be removed also, so I can get a good density measurement for the type of biodiesel I have made. I've made biodiesel using methanol , ethanol , 1-propanol and 2-propanol. The different Types of alcohol produce liquid biodiesel fuels with different properties.

I've taken to using Magnesol again, I think it cleans the biodiesel really efficiently. As for the worrys that using it leaves a mineral compound in the fuel to cause excess engine wear, there is an easy answer - just leave it to settle a few days after mixing.

I recently did some tests doing this, then centrifuging the bio. There was no Magnesol in the fuge after 4 days of settling. I also suspect that using it removes monoglycerides as well as ffa's. The lighter colour of the bio is also very noticeable.

Using Magnesol, then leaving my bio to bleach in the sun a few days gives a colour not too far from pump diesel.

Originally posted by Dgs:I also suspect that using it removes monoglycerides as well as ffa's.

There should not be any FFA's present in biodiesel to remove.

Why do you suspect that Magnasol removes monoglycerides

If the bio has been water washed with the addition of acid then there will be ffa's present.

From tests I have done, monoglycerides increase the cloud/gel point of the bio. If the magnesol treated bio gels/clouds at a similar temp to my water washed fuel where the mono's have been emulsified and removed then I would suspect the magnesol also removes them.

Originally posted by Dgs:If the bio has been water washed with the addition of acid then there will be ffa's present.

Who would do something silly like that???Surely not you.In any event, this discussion is "concerning dry washing with wood chips and/or sawdust" Not water washing with acid.

The quick test for whether magnasol removes FFA's is to titrate some WVO and then do a magnasol "wash" on the WVO and titrate again.If the titration of the WVO drops after the Magnasol wash that is a good indication of what magnasol will do with FFA's.As I recall that has already been posted on the forum but I do not remember the results.

quote:

From tests I have done, monoglycerides increase the cloud/gel point of the bio. If the magnesol treated bio gels/clouds at a similar temp to my water washed fuel where the mono's have been emulsified and removed then I would suspect the magnesol also removes them.

Please describe the testing you performed and results achieved that shows that using magnasol lowers the cloud/gel point of biodiesel by removing monoglycerides.

"removing monoglycerides"? Magnesium silicate removes more polar materials. It absorbs them, as in sticking to its surface. Monoglycerides are a glycerine molecule (polar), but one of the hydroxide groups is an ester group bonded to a fatty acid. That leaves two hydroxide (alcohol) groups on the glycerine backbone of three carbons which can hydrogen bond to magnesium silicate (adhere if that's the right word). A test to determine if monoglycerides that were present are removed would be a spectral analysis. Absorption/emission spectroscopy. Types of molecules (their electron bonds) absorb light energy at a specific wavelength which I believe increases the temperature of the material. But not all wavelengths are absorbed. By measuring absorption/emission of light, electromagnetic radiation before and after purification with magnesium silicate the proof Tilly requests might be obtained. One of those machines to test it are several thousand dollars. Universities with research chemistry departments have them. As far as I know those tests have not been done anywhere.

Unless your making lab size batches I recommend avoiding water altogether, demeth use wood chips in an up-flow and drive on... Why spend time, money and energy for no practical reason? Water, magnesol, centrifuges... bah! Waste of time and money IMO.Also use a biocide if your in an area that gets cold and you need to blend with pump diesel according to the seasons... Dont learn this lesson the hard way like me...The KISS method I use is proven over time and hundreds of thousands of KM's in a common rail CP3 Duramax, a 23HP kubota, various burners etc...Cheers,Jon